Carbon nanotubes (CNTs) are revolutionary materials having valuable electrical, optical, mechanical, and thermal characteristics due to their unique quasi-one-dimensional electron confinement. Despite more than 15 years of R&D, the nanomanufacturing environment for CNTs is still in an inchoate situation. Industrial companies claim they are expanding and refining their processes, yet if one purchases CNTs on the open market, more often than not one obtains a vial of unlabeled, uncharacterized material. Accordingly, current manufacturing processes do not simply produce a single type of CNT. Instead, yields are a mixture of species, along with unwanted chemical impurities (3-50%). Yielding pure nanotubes of a particular species (type) is one of the principal barriers to significant adaptation of single walled nanotubes (SWNTs) in a wide range of industries, including, but not limited to, nanoelectronics, nanobiotechnology, and general nanomaterials (e.g., nanocomposites).
For industrial firms seeking to harness the amazing properties of CNTs, this is an intractable situation. Original Equipment Manufacturers (OEMs) must go to universities or national labs and spend significant time and money to characterize their purchased CNTs prior to end use. Technologies incorporating CNTs thus confront quality issues at every level, ranging from composite manufacturers integrating CNTs into high-strength structures, to the next generation of optical sources, detectors, and displays. Advanced, cost-effective analytical techniques are needed so that CNT manufacturers, product developers, and regulatory agencies can truly “see” what they have and obtain what they truly need.
Fundamental limitations encountered with off-the-shelf instrumentation applied to carbon nanotube metrology include: limits to information attainable; quantitativeness of results; cost, including capital, ownership, and training; complexity of measurement, including sample preparation; system reliability; sample matrices and sample destructiveness. Specifically, instrumentation can require a solution of SWNTs. Measurement repeatability can be a serious issue with solutions, as the SWNTs tend to fall-out of the solution after a single measurement.
Additionally, despite the high number of chemical, electrical and other processes for purification and separation, such as oxidation (e.g. thermal, wet, fixed air, mild), microwave treatment, chemical treatment (HNO3, HCL, mild acid), chromatography, magnetic purification, annealing, filtration, electrophoresis, sonication, centrifugation, there is no current technique that offers a nanomanufacturing-friendly nanotool to the general community. Most all of these techniques have thus far only been demonstrated on lab-scale CNT amounts (a few grams, with some allusion in the respective article that “scale-up should be trivial”), but none of the instruments come in a packaged system for implementation in a nanomanufacturing environment, and moreover many of these purification and separation techniques actually damage or destroy the CNTs during their processing.
Nevertheless, CNTs continue to have a significant allure for materials scientists. Their fundamental properties have been touted to be applicable in a wide range of industries, including chemical, aerospace, automotive, electronics, etc. SWNTs are of special interest to these communities for their prospective properties tunability. The challenge before the industry is to overcome the quality control issue now present at both the raw material supplier and OEM levels. Additionally, there is a challenge of doing this economically and efficiently if commercial manufacturing is to be achieved.
It is therefore desirable to provide systems and methods for quantifying, purifying and separating CNTs. It is also desirable for the systems and methods to be inexpensive and rapid in characterizing SWNTs for the parameters critical to the carbon nanotube industry.